This invention is generally in the field of optical monitoring techniques, and relates to an apparatus for monitoring parameters of workpieces being contained in a cassette. The invention is particularly useful in the manufacture of semiconductor devices for metrology/inspection of wafers progressing on a production line.
The wafers"" manufacture always includes the inspection of wafers after various manufacturing steps, for example after photolithography and chemical mechanical planarization (CMP). Wafers progressing on a production line between various processing tools are located in load and unload cassettes, each cassette containing a number of wafers, usually 25 of 200 mm-diameter wafers. To inspect a specific wafer prior to or after its processing by a specific tool, the wafer should be taken out of, respectively, the load or unload cassette, and brought to an inspection tool, either by an operator or by a robot depending on the kind of the inspection tool used, namely a stand-alone station or an integrated tool (i.e., located within the processing environment).
FIGS. 1a and 1b illustrate (by the way of a block diagram) two different examples of inspecting wafers progressing on a production line, typically employed in FABs.
FIG. 1a exemplifies the part of a production line PL(A), for example associated with photolithography environment containing a phototrack 2, a load cassette 3a, an unload cassette 3b and a robot R which transfers wafers between the photolithography tools. An inspection tool 4a, such as a Scanning Electron Microscope (SEM), is accommodated outside the production line PL(A) as a stand-alone machine. A wafer W to be inspected is brought (handled) to the machine 4 by an operator or robot P, and may then be returned to the production line PL(A).
FIG. 1b illustrates another part of a production line PL(B), for example associated with a CMP tool 6. Here, an integrated inspection tool 4b is used, for example ITM NovaScan 210 model commercially available from Nova Measuring Instruments Ltd, Israel. A robot R supplies a specific wafer W to the tool 4b and brings the wafer to the unload cassette 3b. 
Thus, regardless of whether the stand-alone or integrated inspection tool is used, additional handling of the wafer to be inspected is typically required. Needless to say that the handling of such delicate workpieces as wafers May cause damage to the workpiece and should therefore be avoided. It is especially important in processing wafers of large size, like 300 mm-diameter wafers.
There is accordingly a need in the art to facilitate the inspection/measurement of workpieces progressing along a production line, by providing a novel monitoring apparatus capable of being applied to the workpiece contained in a cassette.
It is a major feature of the present invention to provide such an apparatus whose orientation with respect to the cassette is adjustable in a manner to apply the apparatus to a selected one in a plurality of workpieces contained in the cassette, and to enable scanning of the workpiece.
It is a further feature of the present invention to provide such an apparatus, whose dimensions allow its use as an integrated tool.
The main idea of the present invention is based on the following. Semiconductor wafers are typically kept in a cassette having a plurality of vertically aligned spaced-apart parallel slot-like compartments. Each compartment contains a corresponding one of the wafers in a lot, and a certain gap is typically provided in the slot-like compartment above the upper surface of the wafer contained therein. Thus, in an inspection tool according to the present invention, a probe, which is to be positioned above the wafer during inspection, is designed like an arm insertable into the gap and driven for movement relative to the wafer under inspection. To this end, the probe supporting an optical head is mounted for movement along three mutually perpendicular axes.
Generally, such a monitoring apparatus can be applied to any substantially flat workpiece contained in a cassette, provided a certain gap exists inside the cassette above the workpiece. Moreover, such an apparatus may be any processing tool, e.g., cutting tool or marker, provided the gap size is sufficient for processing the workpiece with this tool.
There is thus provided according to one aspect of the present invention a processing apparatus for applying to a substantially flat workpiece contained in a cassette having a gap thereinside above said workpiece, the apparatus comprising a housing located outside said cassette and a processing tool coupled to the housing, wherein the processing tool is displaceable along three mutually perpendicular axes relative to the cassette for inserting the tool into the gap and moving the tool inside the gap relative to said workpiece.
To provide the above movements of the tool, the apparatus comprises at least one translation assembly. Preferably, the translation assembly guides the movement of the tool along the three axes relative to the housing. However, the construction can be such that a first translation assembly guides the movement of the tool along the two axes relative to the housing, and a second translation assembly guides the movement of the tool along the third axis relative to the cassette, or, alternatively, guides the movement of the housing together with the tool.
Preferably, the processing tool is displaceable between its inoperative position projecting from the housing and an operative position being retracted towards the housing. In the inoperative position of the processing tool, it may be located substantially inside the housing or be folded so as to extend along an outer surface of a sidewall of the housing.
The construction may be such that the processing tool is supported on a single-arm structure projecting from the housing, and this arm is displaceable along the three axes. Alternatively, the processing tool may be supported on a multiple-link kinematic structure, a so-called xe2x80x9cfrog-legsxe2x80x9d, pivotal movements of one or more links providing the displacement of the tool along one or two axes. These pivotal movements may provide the displacement of the tool between its operative position projecting from the housing and an inoperative position being retracted towards the housing.
According to another aspect of the present invention, there is provided an optical monitoring apparatus for monitoring parameters of a substantially flat workpiece contained in a cassette having a gap thereinside above said workpiece, the apparatus comprising a measuring unit located outside said cassette and an optical head carried by a conveyor arm coupled to the measuring unit, the conveyor arm conveying the optical head along three mutually perpendicular axes relative to the cassette so as to insert the optical head into the gap and moving the head inside the gap relative to said workpiece.
The term xe2x80x9cmonitoringxe2x80x9d used herein signifies determining predetermined characteristics of the workpiece by measurements, inspection or metrology technique.
According to yet another aspect of the present invention, there is provided a processing station for processing a substantially flat workpiece which arrives to or leaves the station in a cassette having a gap thereinside above the workpiece, the station comprising processing environment and an optical monitoring apparatus for monitoring the workpiece whilst inside the cassette.
According to some more aspects of the present invention, there are provided an CMP arrangement, a photolithography arrangement and an CVD arrangement, respectively, for processing semiconductor wafers, which utilize a monitoring apparatus for monitoring parameters of the wafers being contained in a cassette having a gap thereinside above the wafer.
More specifically, the present invention is used for monitoring semiconductor wafers (constituting a substantially flat workpiece) with an optical monitoring apparatus (constituting a processing tool) for determining thickness parameters of one or more wafer""s layers, and is therefore described below with respect to this application.